The isolation of small, approximately 100 basepairs, restriction fragments of T7 DNA carrying promotors for the phage-specified T7 RNA Polymerase (single polypeptide chain, MW 100,000) have provided a simple in vitro system to study the mechanism of transcription. A single stranded endonuclease, the T7 gene 3 product, has been isolated and been used to probe the sequence of base pairs melted at the promoter by the T7 RNA polymerase. This endonuclease is potentially a useful probe for all DNA sequences melted by proteins, since it works well at neutral pH and has a 10 to the 2nd power or more fold preference for single stranded DNA. The precise molecular interactions of the polymerase with these promoters will be examined by spectroscopic, chemical modification, radiolabeling and kinetic methods. The molecular properties of T7 RNA polymerase are being determined as well as the sequence of the polymerase gene and hence the amino acid sequence. Multinuclear NMR (1H, 31P and 19F) methods are being used to probe the structure of the complexes of gene 5 protein of bacteriophage fd and gene 32 protein of bacteriophage T4 with oligodeoxy-nucleotides of defined sequence. The role of phosphorylation-dephosphorylation in the structure and function of non-histone chromosomal proteins is under investigation. A non-histone chromosomal protein of MW 55,000 has been isolated which stimulates transcription of nucleosome DNA. Phosphorylation (a single phosphoryl group per monomer) abolishes the stimulation and increases the affinity of the protein for histone. The structure and function of this protein are under investigation.